U.S. utilities that want to connect their customers to the energy data pouring out of their new smart meters face a big problem when it comes to apartments, multi-tenant commercial spaces and other big buildings: the basement-to-dwelling barrier.

Simply put, almost all smart meters being deployed in the U.S. today use ZigBee radios to transmit up-to-the-minute energy data to customers. But in big buildings that house electric meters in basements, there’s no way for these low-power wireless signals to penetrate yards of concrete to reach the individual apartments or suites above.

Utilities are looking at various alternatives to enable their home area network (HAN) or business area network (BAN) plans for such multi-tenant buildings, including using powerline carrier (PLC) technologies like HomePlug Green PHY to transmit data from smart meters to tenants over the same wires that carry electricity. But solutions like these, while being implemented in Europe and Asia, come with extra costs and complications that make them trickier for North American utilities.

Now, a San Diego apartment building is trying out another alternative, using a combination of radio concentrator devices that deliver data to apartments via built-in Ethernet networks, and a cloud-based energy management platform to make sense of it all for tenants. While it’s just a start, it could present an attractive model for utilities in California and elsewhere that are struggling to deliver real-time energy data, and the multitude of pricing plans and demand response programs this could enable, to customers that don’t live in single-family homes.

Vancouver, Canada-based startup Rainforest Automation is supplying the core technology for this San Diego project, in the form of its Link Aggregation Radio Concentrator (LARC) devices. The LARC devices are installed next to the smart meters in the basement, and collect their real-time ZigBee signals, then send them to individual tenants for presentation on in-premise energy monitors, smartphones or other internet-enabled devices.

“Think of it as a gateway that can connect to ten ZigBee radios in meters at the same time,” company president Chris Tumpach told me in an interview last week. “In the case of this building, we plugged the LARC right into the building’s internet, and away we go,” with each individual meter’s data stream being linked to each apartment, so that data streams don't end up in the hands of the wrong tenant.

It helps that the San Diego apartment came prewired with Ethernet connections to each unit, of course. “We see this being used primarily in newer construction, something built in the last twenty years,” he said. “We’re basically looking at going out to developers who have multiple buildings” as a first target market.

But in older buildings that don’t have internet, it might be possible for the building owner or operator to create local Wi-Fi networks that carry the data to tenants’ smartphones or in-home displays, he said. Another possibility is to connect in-home devices via cellular modems to a cloud-based repository of the data that each LARC is pulling from its smart meters, he added.

In San Diego, Rainforest is working with Bidgely, the Sunnyvale, Calif.-based startup that’s built a cloud-based home energy platform that analyzes energy usage data to “disaggregate” individual loads within each dwelling, from HVAC and appliances to TVs and consumer electronics. “If you do want to go to the cloud, to see your data wherever you are or get analytics, then we work with Bidgely to deliver that to consumers,” he said.

California’s big three investor-owned utilities, including San Diego Gas & Electric, may be on the hunt for options like these. The California Public Utilities Commission has asked its utilities to enable smart-meter-to-customer-HAN data exchange as a precursor to rolling out time-of-use pricing to the mass residential market. But that’s been a tricky subject when it comes to apartment dwellers, who after all represent a significant portion of the state’s residential energy customers.

“For this particular solution, if you look in markets like California and Texas, the regulatory framework is ambiguous there,” Tumpach said. While state regulators in both states haven’t yet set specific requirements for linking apartments to smart meter HANs, “There’s a high desire for them to exist.”

Just how tricky this problem can be is evidenced by this particular apartment building’s path to working with Rainforest and Bidgely, he noted. Initially, SDG&E was working with General Electric on a pilot project at the building, meant to link GE’s Nucleus home energy management devices to smart meters. But GE pulled out of the project last year, leaving the utility looking for an alternative solution, Tumpach said.

The next step was to look at PLC “collars” that attached to each smart meter and translated the ZigBee signals into a HomePlug Green PHY format to be sent over the electric wiring, he said. But that technology was deemed too expensive in its present form -- up to $300 per meter for the combination of equipment and costs of having each meter socket retrofitted by an electrician, he said. (It’s important to note that smart meters embedded with PLC technologies, like most being deployed in Europe, shouldn’t face these kinds of extra integration costs.)

Of course, utilities could just ask apartment dwellers and small business tenants in multi-unit buildings to go online and check the energy data that’s collected at the utility. But that back-end data is almost always at least one day old, in contrast to the real-time data being transmitted by the ZigBee radios inside smart meters -- and it’s hard to ask millions of utility customers to agree to real-time pricing programs if they can’t match it with their real-time energy use.